Tag Archives: Darwin

Olivia Judson has written another installment in her series celebrating Charles Darwin. In this one, she suggests that we should lose the term “Darwinism” and all its variants. I think that she argues convincingly that labeling the scientific enterprise of modern evolutionary biology as “Darwinism” implies that the field is static, indeed, “that the subject hasn’t changed much in the 149 years since the publication of the Origin.” Of course, nothing could be further from the truth and the obsession with questions of the form “Was Darwin Right About X?” plays into the hands of anti-rationalist, anti-science creationists.

Frequently, I have been bothered by the cult of Darwin that one finds among a certain kind of evolutionary thinker and it’s nice to see Judson calling this out.

There is an interesting dynamic that played out in the area of human behavioral biology in the late 1980s and early 1990s. At the time, there was a feud developing between scientists who studied the present-day consequences of variation in human behavior and those more interested in the design of the organ that leads to behavior, the brain. In a provocative paper written in 1989, Donald Symons of the University of California Santa Barbara suggested that “adaptive design is usually manifested at the psychological rather than at the behavioral level, that measuring reproductive differentials is at best an inefficient and ambiguous way to illuminate adaptation, and that Darwin’s theory of natural selection sheds light on human affairs only insofar as it promotes understanding of the psychology that underpins these affairs.” (there’s that ownership of natural selection again) Needless to say, this paper did not go over well with people who actually chose to measure the present-day consequences of behavior (e.g., on reproductive success) and a bit of a flame war broke out in the pages of the journal Ethology & Sociobiology (the official publication of the Evolution and Human Behavior Society and later to be renamed Evolution and Human Behavior).

What is so interesting about this debate is how, in good segmentary fashion, the two sides desperately tried to claim Darwin as the founding mythological patriarch of their lineage. A science true to Darwin’s legacy would variously study behavior or study psychology depending upon whether one was a Darwinian Anthropologist or a Darwinian Psychologist (Symons’s terms, though I should note that to this day, at least a plurality of evolutionary psychologists reside professionally in anthropology departments). This debate continues, albeit a little less raw. I list a number of key papers in this debate below. We read these in my graduate seminar on evolutionary theory in the anthropological sciences.

So I support Judson’s call to drop the term “Darwinism” (or “Darwinian”) from our regular scientific vocabulary. As she cleverly argues, we don’t refer to fixed wing aeronautical engineering as “Wrightian” aeronautics, despite the fact that the field was established by the Wright brothers. Use of the patronym plays into the hands of creationists. It also makes it too easy to forget that evolution is effected by more than simply “Darwin’s” natural selection. There is (the other) “Wrightian” genetic drift. Or mutation. Or even something as prosaic as migration (dare I call it “Cavalli-Sforzian”?). Science should strive to transcend the cult of personality. I, for one, would like to see less political and religious jockeying to see which tradition can be more true to its mythological “Darwinian” patriarch and more focus on actually doing science. But I guess that just shows that I remain naïve about human nature.

Olivia Judson’s piece in today’s New York Times makes the important (and chastening) point that too many contemporary biologists have not actually read Darwin in the original. As usual, she is terrific and generally right on. I do have one small issue with a comment she makes:

Natural selection will operate whenever all of three conditions are met. These are: (1) some of the differences between individuals are inherited differences, not due to differences in their environments; (2) more individuals are born than can survive; and (3) part of the reason at least some of the survivors make it is owing to the traits — a longer-than-average beak, say — that they inherited from their parents. For natural selection, then, what is important is that some differences are inherited; and this, Darwin could show.

The problem with this statement is that it’s not actually correct. But it’s incorrect in an interesting way, given Judson’s point that there is value in understanding the history of our science. In the Origin, Darwin was clearly influenced by another foundational document, Thomas Mathus’s Essay on the Principle of Population. Indeed, the Malthusian insight that populations, human or otherwise, can easily outstrip their resource base proved to be a critical link in Darwin’s formulation of the idea of natural selection.

The key about Judson’s statement is that point (2) is not necessary. If it were true, it would imply that natural selection can not act in growing populations. The necessary and sufficient conditions for natural selection acting on a trait are: (i) variation in the trait, (ii) heritability of the trait, and (iii) differential reproductive success as a function of the trait. So a trait can increase even in the absence of differential mortality as long as there is differential fertility. Darwinian fitness is a relative concept. A trait with higher fitness is one that increases in frequency relative to other traits. This increase in relative frequency can come about because of differential mortality or differential fertility or a combination of the two.

It turns out that models of selection are more mathematically tractable when one assumes only viability selection and so this is what is most commonly employed in theoretical work. This relates to the fact that fertility selection works at the level of the breeding pair and not the individual. The equations describing selection in this context thus become rather more complex. But this is more technical than most sane people would care to get. A good review of models of fertility selection can be found in Feldman et al. (1983).

Judson is essentially correct though. We should all have a better understanding of the history of Evolutionary Biology (and, I should add, Anthropology). A major part of this is reading the classics: Darwin, Malthus, Wallace, Fisher, Dobzhansky, Wright, Lorenz, Tibergen, Hinde… I could go on for a while, of course. When I teach my class in life history theory, almost all of the readings are (20th century) classics. My experience in the field is that lots of people cite Hamilton (1966) or Cole (1954), for instance, but very few people have actually read them.

References

Cole, L. C. 1954. The Population Consequences of Life History Phenomena. Quarterly Review of Biology 29 (2):103-137.